1. Field of the Invention
The invention is heat-vulcanizable adhesives, for the bonding of solid substrates, which contain polybutadiene or polybutadiene mixtures and/or copolymers of butadiene with olefins and/or diolefins, and optionally other vulcanizable components. The invention also relates to the use of the heat-vulcanizable adhesives in methods for the bonding of solids, particularly steel sheets for automobile or vehicle assembly.
2. Statement of Related Art
The adhesive bonding of steel sheet in vehicle assembly, and particularly in automobile body assembly, is often done using uncleaned and untreated steel sheet. The adhesive is hardened later in the lacquer drying ovens. Prior to adhesive hardening in the lacquer drying ovens the joined parts will pass through cleaning, phosphatizing, and dip-priming stages. However, the unhardened adhesive can be washed from the glued seam by the aqueous agents used in these process steps. Various measures are known for preventing wash-out of the adhesive. For example, thermal inductive prehardening of the adhesive, use of a solvent-containing adhesive formulation, use of two-component formulation, or use of a strip or a round cord form have been attempted to prevent wash-out. These measures have disadvantages or require the installation of special equipment.
EP-A 0 097 394 (equivalent to U.S. Pat. No. 4,600,745) discloses a heat-vulcanizable polybutadiene-based adhesive which contains, in addition to polybutadiene or a polybutadiene mixture, sulfur, a filler, a water-binding agent (particularly CaO), vulcanization auxiliaries, and vulcanization accelerators. In particular, these adhesives have poor resistance to being washed away in the aqueous cleaning, phosphatizing, and dip-priming stages. The contents of U.S. Pat. No. 4,600,745 are incorporated herein by reference.